Exotic DNA found in the desert offers lessons in the search for Martian life

These organisms are bacteria “so strange and different,” the report states, that the researchers have been unable to identify any known relatives.

“In about half of the cases, the databases couldn’t clearly identify what was on our hands,” lead researcher Armando Azua-Bustos, a microbiologist at the Center for Astrobiology in Madrid, told The Post.

And that brings him back to the Martian analogy: He and his colleagues think the Atacama is a great test bed for the search for Martian life. But the same research done with versions of instruments on Mars rovers today can barely detect microbial fingerprints. Azua-Bustos and his colleagues conclude that this means that finding definitive evidence of current or past life in Martian soil will be difficult without returning samples to Earth.

The research appears to support the long-term Mars exploration strategy of NASA and its partner, the European Space Agency. They are in the midst of a multi-stage mission called Mars Sample Return. If all goes as planned, samples of Martian soil obtained by NASA’s Perseverance rover–which just celebrated its second Mars anniversary–will be returned to Earth sometime early in the next decade for examination in high containment laboratories.

But this new research also highlights the challenges facing scientists who want to know the biological (conjectural) history of Mars. Microbial life, especially if long extinct and fossilized, may exist at or beyond the limit of what can be detected by the kind of instruments small enough to blast off into space and land on another planet.

Scientists have never found an example of life beyond Earth, but the general assumption is that “habitable” worlds will become inhabited — that life emerges, in some way, under the right conditions. The Red Planet has long puzzled astrobiologists. It was more like Earth about 3 billion years ago, when it had a much thicker atmosphere and liquid water on its surface. Plausibly, there is still mysterious life on Mars, although astrobiologists would be happy to find microfossils of something that lived billions of years ago.

NASA’s 1976 Viking mission carried experiments designed to detect life, and one of them provided a promising signal at first, but most scientists concluded that they landed on sterile soil.

Since the Viking mission, NASA has pursued a more incremental strategy focused on finding and exploring sites that show evidence that they might have been habitable billions of years ago, when Mars was much warmer and wetter. Perseverance and its active predecessor, Curiosity, have found traces of organic molecules — the kind of molecules that form the basis of life as we know it — on the surface, though this in and of itself is not evidence of a biological origin.

“The question remains whether it’s meteorite, geological, or biological,” said Amy Williams, a planetary scientist at the University of Florida and a member of the Curiosity and Perseverance Science teams.

The new report from Azua-Bustos and his collaborators is important, Williams said, because it shows that the preservation of organic matter is limited in Mars-like environments and would be difficult to detect even with the most modern laboratory tools.

“This means that detecting organics with spaceflight instruments, such as on current and future Mars rovers, may be more challenging, as organics are easily broken down in the radiation-laden Martian surface environment,” Williams said in an email.

However, the Atacama research shows that even a very arid environment will have layers of sedimentary rock with large amounts of biological detritus, said Chris House, a geologist and astrobiologist at Penn State. “It’s not really a surprise,” he said, “but the results may have shown uniform depression.” This is good news for scientists who hope that dried Martian rocks will yield traces of alien biology.

Azua-Bustos is an Atacama native who spent years making wine before becoming a scientist. He remembers growing up in a town where it only rained once a year, and it was always a highlight. He said that there are places where people have never seen rain and it goes back many generations.

He said he regularly passed through an area of ​​desert, called the Red Stone, on his way to a research site, and one day decided it was worth a closer look. He said the rocks were rust red due to the presence of the mineral hematite, which also represents the red color of Mars.

More than 100 million years ago, in the age of the dinosaurs, the redstone site was a river delta, like the plateau on Mars inside Jezero Crater that Perseverance explores.

Azua-Bustos was surprised by the genetic material of an unusual nature seen in the Atacama research. All life on Earth comes from a common ancestor – as far as we know. There has been speculation, particularly from scientist and author Paul Davies, that life could have originated on Earth more than once and to this day there could be a “shadow” biosphere which is simply too exotic to fit our definition of life on Earth.

However, Azua-Bustos defaults to the less exciting explanation for unclassified organisms: This is genetic material left over from long-extinct life forms that had not been previously documented.

The Perseverance rover continues to explore Jezero Crater, excavating and storing samples of Martian soil. The plan is to place another spacecraft on the surface, which could serve as a launch pad. Perseverance then delivers the samples to the probe, propelling the material into orbit. There you will meet another vehicle, a European-made orbital vehicle, that can deliver precious cargo to Earth For analysis using the best possible laboratory tools.

The new research indicates that this may be the most effective And it may be the only definitive way to find out if anything is alive on Mars.

“We know there are things to discover,” Azua Bustos said. “But if your machine is not designed to be able to detect these things, then we have a problem.”